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When cardiomyocytes are gently warmed to the body‑temperature range (38–42 °C), their sarcomeres begin to oscillate autonomously at 5–10 Hz, close to the natural heartbeat. These oscillations are termed Hyperthermal Sarcomeric Oscillations (HSOs).
This paper provides a detailed analysis of the striking “dual nature” of HSOs:
Period constancy – Although adjacent sarcomeres interact, their oscillation period remains remarkably stable (≈ 7.6 Hz on average).
Chaotic amplitude – In contrast, the amplitude rises and falls chaotically in step with ~1 Hz fluctuations in intracellular Ca²⁺ concentration. Patches of in‑phase and anti‑phase coupling appear irregularly in both space and time.
Lyapunov‑exponent analysis yielded a positive value (≈ 8.8 s⁻¹), and scatter plots of neighboring phases densely filled the phase space, showing that HSOs constitute an ensemble of “nearly phase‑locked chaotic oscillators.” Together with mathematical modeling, the data indicate that such dynamic synchronization fluctuations smooth the summed tension of the sarcomere population, enabling the ventricle to relax instantly even under high‑Ca²⁺ conditions—thus supporting contraction‑rhythm homeostasis. HSOs therefore represent a microscopic control mechanism in which a fixed period (order) and chaotic amplitude (fluctuation) coexist to underpin the robustness of the heartbeat—experimentally demonstrated here for the first time.
A. Schematic diagram of the structure of sarcomere.
B. Changes in the length of adjacent five consecutive sarcomere segments in cardiomyocytes. When the cardiomyocytes are warmed at the timing of the red arrow, HSOs become apparent.
C. Spatio-temporal change in phase of HSOs during heating. On the black horizontal line corresponding to each sarcomere, the phase changes periodically. However, the phase relationship between adjacent sarcomere is changing flexibly. It repeats irregularly in the anti-phase synchronization state like the area surrounded by the white frame, and in the synchronization state like the area not surrounded by the white frame.
Article information & citation
Article information & citation
Seine A. Shintani. Hyperthermal sarcomeric oscillations generated in warmed cardiomyocytes control amplitudes with chaotic properties while keeping cycles constant. Biochem. Biophys. Res. Commun. 611 (2022): 8‑13.
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